1. Field of the Invention
The present general inventive concept relates to an image forming apparatus. More particularly, the present general inventive concept relates to a medium supplying apparatus of an image forming device to pick up and to supply loaded printing media (e.g., paper, transparency or other suitable printing medium) one by one.
2. Description of the Related Art
Generally, an image forming device, such as a copier, a printer, a facsimile, a multifunction machine, or the like, has a function, to form a desired image input from the outside on a printing medium, such as a printing paper. Such an image forming device has a developing unit, a transferring unit, a fixing unit and a medium discharging unit, which are mounted in a main body. In addition, the image forming device has a medium supplying apparatus, which supplies loaded printing media into the main body one by one. An example of such medium supplying apparatus is illustrated in FIG. 1.
Referring to FIG. 1, the medium supplying apparatus includes a medium supplying cassette 10, a knock-up plate 20, a pickup roller 30, and a friction pad 41. The knock-up plate 20 is installed to be movable up and down with respect to the medium supplying cassette 10, and to support printing media. The pickup roller 30 is used to pick up the printing media. The friction pad 41 is used to separate the printing media one by one while facing the pickup roller 30. The friction pad 41 is supported by a supporting holder 42.
To prevent an abrasion (e.g., wear and tear) of the friction pad 41 due to a continuous supply of the printing media, a protecting pad 43 is installed on the supporting holder 42 to come in contact with front ends of the picked-up printing media, as illustrated in FIG. 1.
With the construction as described above, the printing medium supported on the knock-up plate 20 is picked up by the pickup roller 30 to pass over the protecting plate 43 and the friction pad 41, so that the printing medium is separated and conveyed one by one (e.g., one sheet at a time).
However, because of material characteristics of the printing media, the printing media can have a built up electric charge. Thus, static electricity is generated between the printing media and the knock-up plate 20 supporting the printing media. In addition, static electricity is also generated between the pickup roller 30 and the printing media due to friction electrification.
If the printing media loaded on the knock-up plate 20 are relatively small in quantity (e.g., a shorter stack of printing medium sheets), the distance between the knock-up plate 20 and the protecting plate 43 is reduced. Thus, a greater amount of static electricity is generated by electric discharge as the thickness of the stack of printing medium sheets becomes smaller (e.g., as the printing medium sheets get used).
Such generated static electricity during the medium supplying operation can transfer to various parts, such as a controller and the like susceptible to damage by static electricity. As a result, the parts may malfunction, and the image quality may deteriorate.